You can vote twice every 24 hours per internet connection, we really recommend you vote once every 12 hours because sometimes you enter wrong captcha and other things can go wrong as well, we have made tests that show that voting once every 12 hours instead of every 24 hours can give up to a 1/4 more votes.

When we suspect a server of cheating, we instantly 'freeze' the votes of a server. This means the specific server cannot gain any new votes until we've discussed the situation with the server founder. When we've found legitimate proof of cheating, we don't just freeze the votes, but also remove the votes.